GLENDALE, Ariz. -- A woman is recovering after her hair caught fire as she escaped what firefighters are describing as a "hoarder fire" early Monday morning.

It happened in the area just northwest of 45th and Missouri avenues. A man who was out walking his dog at about 5:30 a.m. spotted the fire and called 911.

"This is an extreme hoarding situation which is a hazard for the people living there, for us, neighbors, whoever. This is terrible," said Capt. Mark Coogle with the Phoenix Fire Dept.

It took Glendale firefighters nearly an hour to knock down the fire. They believe the homeowner is a hoarder and say the sheer amount of stuff inside the home made their jobs more challenging than usual.

"When crews got on scene, they had an extremely difficult time getting into the residence," Michael Young of the Glendale Fire Department explained. "We are classifying this as a 'hoarder fire' due to the amount of stuff that the resident had collected. [Firefighters] had a difficult time just getting in through the front door."

Video from the scene showed the front of the house, a pile of debris removed by firefighters outside the front door.

"She is hoarder and she's got lots of her backyard and her house is full of stuff. She can't get in the front door," said neighbor John Hurley who has lived next door to the woman for years.

Firefighters said the scene was still volatile Monday night and said this fire may smolder for days much like a mulch fire.

"Got to dig this stuff up get through it and extinguish it. It's piled to the ceiling," said Capt. Coogle.

The homeowner, a 68-year-old woman, whose name has not been released, was able to escape, but some of her hair caught fire as she did so.

Young described the homeowner as an "elderly female," who has some prior medical conditions. He said she was already outside when crews got to the home. Her injuries reportedly are minor. She was taken to a local hospital as a precaution and is expected to be fine.

Investigators in face masks spent the morning sifting through the rubble, trying to determine what sparked the fire.

While no firefighters were injured in Monday morning's incident, hoarding fires present a unique set of challenges and dangers to crews.

"Many fire departments are experiencing serious fires, injuries, and deaths as the result of compulsive hoarding behavior," according to the National Fire Protection Association. "The excessive accumulation of materials in homes poses a significant threat to firefighters fighting fires and responding to other emergencies in these homes and to residents and neighbors.

"Often, blocked exits prevent escape from the home," the reads the NFPA website. "In addition, many people who are hoarding are injured when they trip over things or when materials fall on them. Responding firefighters can be put at risk due to obstructed exits, falling objects, and excessive fire loading that can lead to collapse. Hoarding makes fighting fires and searching for occupants far more difficult."

Hoarding is a mental illness defined in the Fifth Edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5) as an obsessive-compulsive disorder.

"People with hoarding disorder excessively save items that others may view as worthless and have persistent difficulty getting rid of or parting with possessions, leading to clutter that disrupts their ability to use their living or work spaces," according to the American Psychiatric Association. "Potential consequences of serious hoarding include health and safety concerns, such as fire hazards, tripping hazards, and health code violations."

According to APA, between 2 percent and 5 percent of the population suffers from hoarding disorder.